The Chicago White Sox needed to add another arm before the trade deadline, and general manager Chris Getz did just that on Saturday evening. The move, however, came at a steep price.
The White Sox acquired right-hander Luis Castillo from the Seattle Mariners in exchange for reliever Seranthony Domínguez, outfielder Nolan Jones and catcher Boston Smith, the organization’s No. 15-ranked prospect.
Reports indicated the White Sox were willing to absorb salary in exchange for a pitcher with multiple years of club control, and this deal checks both boxes.
Castillo is under contract through at least the 2027 season, with a $25 million vesting option for 2028 if he reaches 180 innings in 2027. If he misses 130 or more days due to a UCL injury, however, that vesting option converts into a $5 million club option, providing the White Sox with added protection against a significant arm injury.
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While the White Sox were able to get Dominguez’s two-year $20 million contract off the books, they also took on a significant financial commitment. Chicago will be responsible for Castillo’s full $22.75 million salary this season and another $22.75 million in 2027.
In essence, Chicago traded a proven but struggling reliever in Domínguez for a proven but struggling starter in Castillo, while also absorbing significant additional financial obligations and parting with a prospect who had just reached Double-A and was putting together a solid season in the minors.
Teams are bound to overpay for pitching at this time of year, and that is simply the nature of the trade market. However, taking on Castillo’s salary while also surrendering Smith makes this a risky deal that could ultimately prove to be an overpay by the White Sox.
But let’s start with the positives.
Castillo fits the profile of several arms the White Sox were reportedly targeting, such as New York Mets right-hander Freddy Peralta and Baltimore Orioles southpaw Trevor Rogers. Established starters with a proven track record who are in the midst of down seasons.
For the better part of Castillo’s ten-year MLB career, he has been viewed as an ace. He is a three-time All-Star who finished fifth in the Cy Young voting in 2023 and owns a career 3.65 ERA. There is also no denying that the 33-year-old is a workhorse.
He led the MLB in games started in 2021 and 2023 and has thrown 170-plus innings in six of his ten seasons, averaging over 150 innings thrown a season. This is especially valuable for the White Sox, who have not been able to get much length out of Noah Schultz or Erick Fedde at the bottom of the rotation.
Castillo’s durability figures to be a major factor as to why the White Sox pulled the trigger, but the red flags this season are hard to overlook. His strikeout rate, once one of the strengths of his game, has fallen off significantly. The Dominican right-hander has posted a 25% strikeout rate for his career, well above the MLB average, but that number has dipped to just 19% this season.
One of the biggest reasons why is that he has abandoned his changeup, which was once one of his most lethal weapons. In 2019, his changeup generated a 28 run value, produced a 47% strikeout rate and limited hitters to a .133 expected batting average.
However, that dominance has steadily faded since 2022, and Castillo has responded by turning to the pitch less frequently. This season, he has thrown his changeup at just a 13% clip, largely because opponents are posting a .345 expected batting average against it.
If Brian Bannister and the White Sox pitching lab can help unlock that changeup once again, there is reason to believe that Castillo can return to form. After all, he is only one year removed from posting a 3.54 ERA across 180.2 innings.
Unfortunately, the reduced strikeout rate isn’t the only red flag. Opponents have been hammering him this season, and Castillo has struggled to keep the ball on the ground. His average exit velocity, barrel percentage and ground-ball rate all rank in the bottom half of MLB, concerns that are only amplified in a hitter-friendly park like Rate Field.
The move would have been much more palatable if the White Sox weren’t forced to part with Boston Smith.
Jones was on a minor league contract and had yet to play a game for the White Sox this season, while Dominguez’s struggles out of the bullpen have been well documented this season.
After being signed to be the White Sox primary closer, Dominguez was jettisoned from the role after converting only 12 of his 17 save opportunities while posting a 3.99 ERA. However, there were signs that he was beginning to return to form. In his last seven appearances, he recorded seven strikeouts in 5.2 innings while allowing just one run. Still, given his inconsistency this season, you can live with giving up those two and taking on the salary for a pitcher with Castillo’s track record.
If the trade had only involved Smith, Domínguez and Jones, it would have been a strong deal for the White Sox. Even if Chicago had simply moved on from Domínguez and Jones while absorbing Castillo’s salary, the move would have been much easier to justify.
But when you have to include Smith, a player who the White Sox had just acquired for Curtis Mead in a trade with the Tampa Bay Rays and was hitting .291 with a 1.037 OPS across three different levels in the minor leagues this season, the price is a bit more difficult to stomach.
Ultimately, you have to give credit to Getz for being aggressive. The American League is wide open, and the White Sox have a rare opportunity to compete for a pennant. When a window like this opens, teams cannot afford to let it pass by because there is no guarantee another one will come around anytime soon.
Castillo does provide the rotation a boost, will help the bullpen by being able to take on innings, and could be a prime candidate to benefit from a change of scenery. But Castillo alone does not move the needle enough for the White Sox to be considered a legitimate World Series threat. If more moves are coming, the risk becomes much easier to justify. If not, the White Sox may have overpaid for a pitcher who only marginally improves their postseason chances.
